Software

Software

1. Interfaces

   • User Interface Software
     • an operating system must provide a way for the user to interact with the computer
     • the user interface is the boundary between the human and the machine
   • The Interface
     • Lets the user give commands
     • Asks questions
     • Displays a response
   • Command Line Interface (Terminal)
     • The interface requires the user to type commands. The commands are translated by a command interpreter so the computer can understand.
     • You can control the entire computer system with commands
     • Technicians prefer to group commands together to carry out maintenance jobs automatically
     • A shell is a software that a user needs to be able to communicate with the kernel
   • Graphical User Interface (GUI)
     • Uses icons to represent sources, files, programmes and actions.
     • E.g. Windows computer, iPad
     • Pros:- -No special training needed -keyboard use is limited -no commands needed to work on it
   • Touch screen interface
     • Some interfaces are designed for smart phones or tablets there's are not made for mouse input
     • Some laptops have integrated touch screen interfaces
   • Natural language + speech
     • Some interfaces accept normal speech as an input.
     • This is difficult because:- -accents -speed of taking -dialect use -clarity of diction

2. Memory management

   • Virtual memory
     • A "not real memory"
     • It uses secondary storage to hold parts of the program that aren't immediately needed
     • It's slower to access the main memory. A large program may take up too much memory to its divided into models
     • The modules are stored separately in secondary storage
     • When it's needed it's taken back from the secondary storage
   • Peripheral management
     • A file is a named store of data on a secondary storage media
     • The OS is responsible for keeping track of all files in a system. The are copied into main storage when needed
     • The OS must know exactly we're the files are located.
   • Fragmentation + defragmentation
     • Fragmentation is when a file has been taken apart and stored in different locations in the hardware
     • Defragmentation is when a file is put back together after being fragmented. It's organised into size order
   • Device drivers
     • The OS has to take control of all the input and output from the system.
     • Creates the interface, allows an OS to communicate with the device, allows device to operate

3. File systems

   • The OS systems organise all the files in secondary storage. Most use a hierarchal system
   • File extensions
     • .doc
     • .mp3
     • .txt
     • .html
     • .mp4
   • File attributes
     • Files can be given different attributes which provide extra information
       • How big is the file When was it last modified? Who made it?

4. Viruses/ Security

   • Viruses
     • Viruses are programs that replicate themselves. They can attach themselves to a legitimate program
     • They damage files, take control of the computer, retrieve data
     • Some viruses have no payload but can still cause damage
   • Security
     • Authentication
       • OS usually allows the authentication of users . This means they are set up to check the the users are who they say they are
       • Password, user name
   • Privileges
     • Privileges are rights assigned to users and groups
     • Read, write or execute a file
   • Encryption
     • Some files are encrypted meaning an unauthorised person cannot access the files encrypted

5. Programming software

   • Editors
     • Editors or text editors are like cut down word processors. Don't correct gramma
     • They don't save extra characters such as formatting information
     • Good for sourcing code in programming
   • Linkers + interpreters
     • Linkers combine modules of object code (compiling)
     • Interpreters convert typed commands into machine instructions
   • Applications + utilities
     • Apps are programs that person use for specific purposes e.g word, bar code scanner
     • Utilities are software tools that help maintain the system.
       • Antivirus, spyware, firewalls

6. Types of software

   • Custom written software
     • Custom written software is designed to a customs preference
     • Pros:- -it should have the exact features the customer wants - the developer may provide training
     • Cons:- -can't text it -it's expensive
   • Off the shelf software
     • It can be brought from a supplier already boxed up and ready to install
     • Pros:- -ready immediately -it's been tested -cheaper
     • Cons:- -won't have everything the customer requires -it might need extensive customisation
   • Open source software
     • This software is in the public domain by the programmers (e.g Linux, Firefox)
     • Pros:- -free -can be altered -reliable
     • Cons:- -no maintenance contract -no contract if there are problems
   • Proprietary software
     • This is developed to benefit/ profit a company (E.g word, PowerPoint)
     • Pros:- -somewhere to go if there is a problem - has been tested
     • Cons:- - it can be expensive -deliberate incompatibilities
   • Software procurement
     • Software can be obtained from various resources systems managers must make choices so that their organisation gets a system.